Zoolander is not the type of movie you like instantly, it's the kind that grows on you. The more you see it, the funnier it gets. The piece is not kind on the fashion industry and least of all on male models, but it's fun as hell.
It's difficult to explain what is good about it when you can't name any single aspect as a commanding thread. The enjoyment itself derives from a number of little things. The whole walk-off scene is a good example. The editing isn't miraculous but it's right. The music isn't perfect, but it's good. The acting isn't superb, but it works well. It's the meshing of every little pieces that makes that scene and its sarcasm totally hilarious.
In the known actors, we have a long list: Ben Stiller, Owen Wilson, Christine Taylor, Will Ferrell, Milla Jovovich, Jerry Stiller, David Duchovny, Jon Voight, Vince Vaughn, David Bowie, Donald Trump, Christian Slater, Tom Ford, Cuba Gooding Jr., Tommy Hilfiger, Natalie Portman, Fabio, Lenny Kravitz, Gwen Stefani, Heidi Klum, Paris Hilton, Lil' Kim, Winona Ryder, Claudia Schiffer, Karl Lagerfeld, Donatella Versace, Victoria Beckham, Stephen Dorff, Jennifer Coolidge, James Marsden, Patton Oswalt and Billy Zane.
You want to see something offbeat, with odd humor, a silly story, and plenty of caricatures? This is probably a good movie for you.